1. Field of the Invention
The present invention relates to a lighting device, and more particularly, relates to a lighting device which is suitably used as a lighting unit of a lighting apparatus configured by assembling the lighting unit and an apparatus body.
2. Description of the Related Art
There has been suggested a lighting apparatus (for example, see JP-A-2012-104257) configured by assembling a lighting unit and an apparatus body, and a lighting device (for example, see JP-A-2011-151218) suitably used as a lighting unit. FIG. 5 shows such a lighting apparatus as an example. The lighting apparatus 100 includes a lighting unit 110 having an approximately cylindrical shape, and an apparatus body 120 to which the lighting unit 110 is assembled. The lighting unit 110 includes a frame 101, a light source unit 104, and a lens 105. In the lighting unit 110, the lens 105 is attached to a front side of the frame 101, and the light source unit 104 including a substrate 103 and a light emitting device 102 mounted on a mounting face 103a of the substrate 103 is attached to a rear side of the frame 101 such that light emitted from the light emitting device 102 is directed to the front side. The apparatus body 120 includes a ring-shaped housing 112 which surrounds a side surface 106 of the lighting unit 110 when the lighting unit 110 is assembled, a heat radiation member 114 provided to cover an opening of one side of the housing 112.
In the lighting apparatus 100 shown in FIG. 5, the side surface 106 of the frame 101 is provided with a plurality of protrusions 107, and an inner surface 113 of the housing, 112 is provided with engaged portions 115 corresponding to the plurality of protrusions 107, respectively. During the use of the lighting apparatus 100, the lighting unit 110 is assembled in the housing 112 such that each protrusion 107 is engaged with the corresponding engaged portion 115. The lighting apparatus 100 is configured such that the heat radiation member 114 is in contact with a rear surface 103b of the substrate 103 when the lighting unit 110 is assembled in the housing 112, so that heat generated from the light emitting device 102 can be efficiently radiated.
However, in the lighting apparatus 100 shown in FIG. 5, if a dimensional accuracy of formation positions of the engaged portions 115 or the protrusions 107 is low, the contact between the heat radiation member 114 and the rear surface 103b of the substrate 103 of the light source unit 104 becomes insufficient. That is, for example, a state (partial contact) in which only a part of the rear surface 103b is in contact with the heat radiation member 114 may occur. If such a state occurs, the heat generated from the light emitting device 102 cannot be efficiently radiated to the heat radiation member 114, a temperature of the light source unit 104 rises, and a luminous efficiency of the light emitting device 102 is reduced accordingly.